1. Field of the Invention
The present invention relates to a polyethersulfone fiber, a production method thereof, and a filter.
2. Description of the Related Art
In a semiconductor production, a filter having strong resistance to chemical liquids (containing organic solvents, acids, alkalis, oxidizers and the like) and being difficult to arise elution substance from a filter has been demanded. As the filter with such characteristics, microporous microfiltration membranes made of a polytetrafluoroethylene (PTFE) have conventionally been used widely. However, since the PTFE is expensive, the production cost tends to be increased, particularly when such the membrane such as the microfiltration membrane is prepared from the PTFE and utilized in the semiconductor production and the like. In recent years, investigations are made on the use of a more inexpensive polyethersulfone for the filter, instead of using the PTFE (see JP-A-2002-166144).
The polyethersulfone, however, tends to be difficult to be made into a fiber having a small fiber diameter. Such a filter of polyethersulfone fiber having not so small fiber diameter may be difficult to sufficiently trap fine particles, and therefore, is sometimes not appropriate for the microfiltration membrane used in the semiconductor production.